It was shown in recent works that O-mode reflectometry is a powerful diagnostic to determine the time-frequency evolution of Alfvén Eigenmodes (AEs) on the JET tokamak. Due to the fact that the density profile is generally flat in the plasma core region where the AEs are localised, the best way of detecting these modes was to use a probing wave with frequency higher than the cut-off frequency (i.e. when the diagnostic acts as an interferometer). Although such line-integrated measurements exhibit an unprecedented time and frequency resolution, they cannot provide direct radial localisation of the AEs. To overcome this limitation, X-mode reflectometry is a promising option. This paper reports on the first successful localised X-mode reflectometry measurements of AEs on JET, recently obtained with the benefit of new low-attenuation transmission lines installed under the EFDA enhancement project "Millimetre Wave Access".